1. Field of the Invention
This application relates to blood pumps such as left or right ventricular assist devices with an expandable impeller for treatment of heart disease. Still more particularly, this application relates to expandable cannulas for use in such blood pumps, and to other structural features of these devices.
2. Description of the Related Art
Heart disease is a major problem in society, and claims many lives per year. After a heart attack, only a small number of patients can be treated successfully and non-invasively using medicines, such as pharmaceuticals. However, with sufficient mechanical assistance to the heart function, a majority of patients may recover from a heart attack, including those with cardiogenic shock.
In a conventional approach, a blood pump having a fixed cross-section is surgically inserted within the left ventricle of the heart and the aortic arch to assist the heart in its function. Surgical placement is required, since it is presently impractical or impossible to percutaneously insert a pump of the size needed for sustaining adequate blood flow. The object of the surgically inserted pump is to reduce the load on the heart muscle for a period of time, which may be as long as a week, allowing the affected heart muscle to recover while healing in a substantially unloaded state.
Surgical insertion, however, can cause additional serious stresses in heart failure patients. Accordingly, devices have been developed which are capable of percutaneous insertion while at the same time providing an adequate amount of blood flow. Such devices, including those described in U.S. Pat. No. 7,393,181 and pending Application No. 11/728,051, the disclosures of which are hereby incorporated by reference herein, have a sufficiently small diameter to be inserted percutaneously through a femoral artery, but may subsequently be expanded in diameter so as to generate a sufficient sustaining blood flow.